Current therapy for Rheumatiod arthritis comprises non-steroidal anti- inflammatory drugs (NSAIDs) in early stages of the disease, ultimately given way to oral steroids and the disease-modifying anti-rheumatic drugs (DMARDs) as the disease progressively worsens. Methotrexate (MTX) has become the DMARD of choice of many rheumatologists because of its faster mode of action and better record of prolonged use. However, despite the use of high doses of MTX, many patients only experience partial relief of symptoms and still have features of active disease. Experimental evidence implicates TNF as an important mediator in the pathobiology of RA and underscores TNF as an appropriate therapeutic target. Chimeric A2 (cA2) is a monoclonal antibody that binds with high affinity and specificity to human TNF and neutralizes its biologic activity. The current trial is designed to show in a larger patient population (n=300) that cA2 given for up to one year will provide a rapid and sustained reduction of clinical signs and symptoms of RA in patients who have active RA despite MTX therapy. Four cA2 treatment groups will be evaluated and compared to a placebo group. The primary endpoint in this study will be a reduction in the clinical signs and symptoms of RA at 30 weeks following the onset of treatment. Continuing reduction in signs and symptoms, as well as disability, joint damage, disease remission and quality of life will be evaluated at 1 year.